Zinc base alloy



Patented July 21, 1936 PATENT OFFICE zmc BASE error I Willis M. Peirce and Edmund A. Anderson, Palmerton,.Pa., assignors to The New Jersey Zinc Company, New York, N. Y., a corporation of New Jersey No Drawing.

Application -Ma'rch 12, 1929,

Serial No. 346,493

4 Claims. (01. 75-178) This invention relates to wrought or mechani cally worked zinc products, such as rolled sheet or strip zinc, and has for its principal object the provision, as a new article of manufacture, of an improved wrought zinc product. In a broader aspect, the invention contemplates the provision of improved zinc base alloys capable of being mechanically worked to produce wrought zinc products possessing superior resistance to cold flow.

Zinc, like other metals of relatively low-melting point, undergoes slow plastic deformation or cold flow when subjected continuously to loads as low as a quarter of the ultimate tensile strength as measured by ordinary tensile testing methods. All wrought or mechanically worked zinc products made of high grade or common zinc metal are readily susceptible to such plastic or progressive and permanent deformation under constant and continuously applied loads materially below the ultimate tensile strength,a phenomenon frequently designated as cold flow. In other words, at ordinary temperatures a continuously applied constant load (far below the ultimate tensile strength as determined by ordinary methods) causes permanent deformation in the heretofore available wrought zinc products of commerce. Under sufliciently low continuous loads the rate of progressive deformation becomes so small as to be unmeasurable by known methods, if not actually reaching the zero value, and such low or negligible loads may be interpreted as safe working stresses for these heretofore available wrought zinc products when used as structural materials, for example, in the form of corrugated sheets. From the structural engineers viewpoint, however, these wrought zinc products have so low a safe working stress, as determined by actual invention possess improved economic advantages over the heretofore available zinc products of the same general type. A further aim of the invention is to provide improved zinc base alloys capable when appropriately wrought of producing 6 the improved wrought zinc products of the invention.

In the production of rolled zinc, either by strip rolling or pack rolling, the properties of .the finished rolled strips or sheets depend upon the com- 10 position of the zinc metal as well as upon the rolling practice. Thus, a high grade zinc metal, such as the well-known Horsehead or other high grade brands, yields a very soft and ductile strip or sheet under appropriate conditions of rolling. On the other hand, the more common grades of zinc metal, such as the well-known Prime West em or other grades of common metal, which are natural alloys of zinc, lead and cadmium containing higher percentages of cadmium than prescut in high grade-zinc metal, yield when rolled under appropriate conditions a stiffer and harder 'product than can be obtained from high grade zinc metal.

The stifier strip or sheet rolled from common zinc metal possesses for certain purposes distinct advantages over the softer product rolled from high grade zinc metal. For example, one of the uses of rolled zinc is in the fabrication of corrugated sheets for roofing and siding purposes on buildings. Here resistance to cold flow is of great importance, since it determines the gauge of zinc necessary to give adequate strength and resistance to plastic deformation when the sheets are laid on the building purlins.

Our investigations and experiments have indi cated that the increase in the resistance to cold flow which can be secured through solid solution forming alloying elements, such as cadmium and copper, is limited, and we have, therefore, experimented with alloying elements which introduce aseparate hardening constituent or constituents into the structure of the ultimate zinc base alloy. We have investigated a very large number of zinc base alloy combinations in the wrought form and 45 have found that the resistance to cold flow can be very substantially increased when the zinc base alloy is of appropriate composition. We have, we believe, discovered thev principle upon which zinc base alloys should be compounded for 0 the purposes herein contemplated, and our present invention is, to a large extent, based upon this discovery.

It is a known fact that the resistance to cold flow of wrought zinc products may be increased to a slight and limited extent by the addition of elements which form a solid solution with zinc-in, percentages which enter completely into'solidsolution. As hereinbefore mentioned, the natural impurity cadmium found in common zinc metal produces such an effect. No other single element has been found which, entering into solid solution with zinc, produces a suificiently greater effect. to be of commercial value. Neither does there appear to be any combination of elements which when added to zinc in percentages within normal solid solubility limits in'their respective binary systems produces economically important improvements in the resistance to cold flow.

zinc base alloy, having one or more metallic elements in solid solution, of another metallicelement (or elements) in an amount 'greatenthan itssolid solubility in zinc (i. e. in binary association with zinc) at ordinary room temperature,

an economically important increase in the resistance to cold fiow of the mechanically worked alloy may be effected. The first element (or elements) present in solid solution in the zinc, appears to produce a slight increase in the resistance to cold flow'of the alloy. This element (or elements) may be present in amount exceeding its limit. of solid solubility in zinc, but .need: not

necessarily be present in such amount. The second element (or elements) may have no or a limited solid solubility in zinc, but-must be present in the zinc base alloy in an amount exceeding its limit of solid solubility in zinc. The second ele-, ment (or elements) is present'in the alloy as a second constituent (or constituents) in which it may becombined with zinc or with the first element or with the two jointly. The function of. the second constituent (or constituents) appears to be to produce a very substantial increase in the resistance to cold flow by hindering slip within or between the crystals.

Our present invention thus comprises a..me-. chanically worked zinc base'alloy (as well as thel alloy itself) possessing marked resistance to coldfiow brought about by alloying zinc. with other metallic elements, one of which goes into solid. solution in the zinc to a measurable extent and. another of which is present in the alloy in an amount greater than its limit of solid solubility in binary association with zinc at ordinary room temperature, say 20 C. For the purposes of the invention, a zinc base alloy is to be understood as 1 one consisting principally of zinc, say, for example, not less than zinc and preferably not less than zinc. The metallic element (orelements) in solid solution in the zinc may be copper, cadmium, manganese, aluminum and probably others. Of these we have secured-the most satisfactory results with copper, cadmium and manganese. While aluminum produces'the desired increase in resistance to cold flow, its tendency to cause intercrystalline oxidationupon aging impairs its practical utility for the purposes of the invention. The metal present in excess of its limit of solid solubility in zinc may be mag-- 75. zincproducts of theinve'ntion made gro n, zinc smear We have discovered that by the addition toa flow to wrought products made therefrom. The

balance of alloy No. 1 was common zinc metal containing 0.15% cadmium, while the balance of each of the other alloys was high grade metal.

Tabulatzon Resistance to wrought prod- 4 uct. Time in Composition of metal from which wrought product minutes to prowas made duce 10% elongetion under static tensile load of 10,000

lbs. per sq. in.

High grade zinc metal 480 ommon zinc metal 3,000 Alloy No. 1.- 1% Cu; 0.15% Cd; 0.01% Mghoveiz- 43, 000 Alloy No.---2. 1% Cu; 0.01% Mg over" 50, 000 Alloy N0. 8. 1% Cu; 0.4% Mn 65,000 Alloy No. 4. L% Cu; 0.05"}, L1 80,000 Alloy No. 5. 1% Cu; 0. 69. 000 Alloy No. 6. 1% Cu; 0 50. 000 Alloy No. 7. 1% Cu: 0 50. 000 Alloy No. 8. 1% Cu: 0 50. 000 Alloy No. 9. 0.55%C'd70 01 0 21. $0 Alloy No. 10; 0.55% (dz 0.05"} 50. 000 Alloy No. 11. 0.55; (d: 0.3; Ni. 14.600 Alloy No. 12. 0.5% M11; 0.01;- .\ig .u\'or. 21.000

In thej f oregoing tabulation. the resistance to coid' fiow or the various wrought zinc products was determined by static tensile tests and is expressed in minutes. The static tensile strength may beconvenintly measured by applying a produce 10% elongation in a standard test speci men at a. temperature of 20-25 C. with a dead load calculated to give a'stress of 10,000 pounds per square inch on the original section of the test specimen. The standard test specimen was a representative sample of the wrought zinc product (rolled sheet zinc in these instances), 0.032 inch thick, 2 inch gauge length, inch reduced section width, 1 inch wide grips, and 1 inch radius fillets.

The percentages of the alloying elements present in the zinc base alloy are susceptible of variat ion over a certain range, rather diflicult of exact definition. While it is essential that the alloy contain such amount of the hardening constituent' (or'constituents) as will introduce thedesired slip resistance, an excessive amount of any such7: onstituent,.whether resulting from an exc'jess of the first element beyond its solid solubility limit in zinc or from too large an addition of the second element beyondits solid solubility limit in. zinc, may affect the ,alloy .unfavorably in respect to either its mechanical working properties or its resistance to cold flow. It has been our experience, particularly with respect tocopper. that the best results are usually attained by including the-alloy such a percentage of the first is about 1%.

manganese present, as the first element, considerably in excess of its limit of solid solubility in zinc. Subject to these considerations,'we believe that, with appropriate methods of mechanical working, the alloying elements mentioned in the foregoing tabulation may vary within the following limitsz-copper or from 0.05 to 2% and possibly to 5%; manganese (as first element within limit of solid solubility in zinc) from 0.01 to 0.1%, and (as second element exceeding limit of solid solubility in zinc) from 0.1 to 2%; magnesium or lithium from 0.005 to0.5%; and nickel from 0.05 to 1%.

The zinc base alloys of the invention may, be compounded in any approved manner. Either high grade zinc metal relatively free from lead and cadmium or lower grade zinc metal containing natural or usual amounts of lead and cad"- mium may be used as the zinc base. The norinal lead and iron content of either high grade or common zinc metal uses not unfavorably affect those properties of the alloy with" which the invention is particularly concerned. How ever, taking all factors into consideration, we have found that the optimum results are ordinarily attained when thezinc base is high grade zinc metal. We have secured unusually satisfactory rolling properties with alloys inwhich the zinc base was a very high grade zinc'metalcontaining less than 0.01% total impurities.

While the zinc base alloys of the invention. can be wrought or mechanically worked by themethods or'practices heretofore customary in mechanically working high grade or common zinc metals, it has been found that these methods and practices do not ordinarilyproduce wrought zinc products of that superior iesistanceto cold flow which these zinc base alloys are capable of developing under more suitable methods of mechanical working. In general, it may be said that the mechanical workingji f the zinc alloy should be so conducted aa not to cause any substantial condition of work hardening in the finished wrought product, if the maximum resistance to cold flow is to be developed. To this end;

Willis M. Peirce has disclosed in his copending' patent application, Serial No. 347,195,filed March 14, 1929, a method of developing superior resistance to cold flow in wrought zinc products. made from the zinc base alloys of the invention which involves hot working of the alloy, at temperatures above (2., throughout or during the final stages of the working treatment, with the view of substantially inhibiting any condition of work' heating (preferably in 20 seconds or less) the wrought zinc product (made of a zinc base alloy of the invention) to the predetermined elevated temperature of heat treatment (preferably in the neighborhood of ZOO-400 C.) and holding the product at that temperature for a suflicieut length 3 of time'to remove any condition of work hardening therein.

The wrought zinc products of the invention may be made or fabricated by any operation involving mechanical working of the zinc base alloy. .Thus, the mechanical working may be rolling, drawing, extruding and the like or may be punch-press or forming operations such as drawing. extruding, squirting, spinning, bending,

, condition of workhardening, for the purpose of improving certain physical properties, such as dynamic ductility, essential to the successful conduct of various subsequent fabricating or forming operations, such as punch-pressing etc.

The improved zinc products of the invention possess very superior physical properties as compared with heretofore commercially available wrought zinc products. We have already emphasized the importance and economic advan-.

. tages of the superior resistance to cold flow.

This property imparts to the products of the invention a safe working stress under a continuously applied load very substantially greater than is possible with any heretofore available wrought zinc product. The improved physical properties of the zinc products of the invention make them useful in many fields and for many purposes where the heretofore available wrought zinc products have not been used, as well as greatly superior to the wrought zinc products which have been heretofore used, such as zinc roofing and the like.

We claim:

1. A zinc base alloy capableof being mechanically worked to produce wrought products possessing superior resistance to cold flow, said alloy containing from .05 to 2% copper and at least one metal selected from the group consisting of manganese and nickel, the manganese when incorporated in the alloy being from .1 to 2% and the nickel when incorporated in the alloy being from .05 to 1%, substantially all of the balance being zinc. I

2. A zinc base alloy capable of being mechanically worked to produce wrought products possessing superior resistance to cold flow, said alloy containing from .1 to 2% copper and at least one metal selected from thegroup consisting of manganese and nickel, the manganese when incorporatedin the alloy being from .1 to 25% and the nickel when incorporated in the alloy' being from .1 to 25%, substantially all of the balance being zinc.

3. A zinc base alloy capable of being mechanically worked to produce wrought productspossessing superior resistance to cold flow, said alloy containing from .05 to 2% copper, from .005 to 5% magnesium, and at least one metal selected from the group consisting of manganese and nickel, the manganese when incorporated in the alloy being from .1 to 2% and the nickel whm incorporated in the alloy being from .05 to 1%,

substantially all of the balance being zinc.

an zinc base alloy capable of being mechanically worked to produce wrought, products possessing superior resistance to cold flow, said alloy containing from .05 to 2% copper, from .005 to .5% lithium and at least one metal selected from the group consisting of manganese and nickel, the manganese when incorporated in the alloy being from .1 to 2% and the nickel when inincorporated in the alloy being from .05 to 1%, substantially all of the balance being zinc.

WIIJZJS M. PEIRCE. EDMUND A. ANDERSON. 

